#include <Arduino.h>
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/*
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WiFiTelnetToSerial - Example Transparent UART to Telnet Server for esp8266
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Copyright (c) 2015 Hristo Gochkov. All rights reserved.
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This file is part of the ESP8266WiFi library for Arduino environment.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <ESP8266WiFi.h>
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#include <algorithm> // std::min
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#ifndef STASSID
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#define STASSID "ZyXEL5500bT5"
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#define STAPSK "eBusgxczl5"
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#endif
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/*
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SWAP_PINS:
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0: use Serial1 for logging (legacy example)
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1: configure Hardware Serial port on RX:GPIO13 TX:GPIO15
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and use SoftwareSerial for logging on
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standard Serial pins RX:GPIO3 and TX:GPIO1
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*/
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#define SWAP_PINS 0
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/*
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SERIAL_LOOPBACK
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0: normal serial operations
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1: RX-TX are internally connected (loopback)
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*/
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#define SERIAL_LOOPBACK 0
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#define BAUD_SERIAL 115200
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#define BAUD_LOGGER 115200
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#define RXBUFFERSIZE 1024
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////////////////////////////////////////////////////////////
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#if SERIAL_LOOPBACK
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#undef BAUD_SERIAL
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#define BAUD_SERIAL 3000000
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#include <esp8266_peri.h>
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#endif
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#if SWAP_PINS
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#include <SoftwareSerial.h>
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SoftwareSerial* logger = nullptr;
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#else
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#define logger (&Serial1)
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#endif
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#define STACK_PROTECTOR 512 // bytes
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//how many clients should be able to telnet to this ESP8266
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#define MAX_SRV_CLIENTS 2
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const char* ssid = STASSID;
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const char* password = STAPSK;
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const int port = 23;
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WiFiServer server(port);
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WiFiClient serverClients[MAX_SRV_CLIENTS];
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void setup() {
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Serial.begin(BAUD_SERIAL);
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Serial.setRxBufferSize(RXBUFFERSIZE);
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#if SWAP_PINS
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Serial.swap();
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// Hardware serial is now on RX:GPIO13 TX:GPIO15
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// use SoftwareSerial on regular RX(3)/TX(1) for logging
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logger = new SoftwareSerial(3, 1);
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logger->begin(BAUD_LOGGER);
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logger->println("\n\nUsing SoftwareSerial for logging");
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#else
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logger->begin(BAUD_LOGGER);
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logger->println("\n\nUsing Serial1 for logging");
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#endif
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logger->println(ESP.getFullVersion());
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logger->printf("Serial baud: %d (8n1: %d KB/s)\n", BAUD_SERIAL, BAUD_SERIAL * 8 / 10 / 1024);
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logger->printf("Serial receive buffer size: %d bytes\n", RXBUFFERSIZE);
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#if SERIAL_LOOPBACK
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USC0(0) |= (1 << UCLBE); // incomplete HardwareSerial API
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logger->println("Serial Internal Loopback enabled");
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#endif
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WiFi.mode(WIFI_STA);
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WiFi.begin(ssid, password);
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logger->print("\nConnecting to ");
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logger->println(ssid);
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while (WiFi.status() != WL_CONNECTED) {
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logger->print('.');
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delay(500);
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}
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logger->println();
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logger->print("connected, address=");
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logger->println(WiFi.localIP());
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//start server
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server.begin();
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server.setNoDelay(true);
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logger->print("Ready! Use 'telnet ");
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logger->print(WiFi.localIP());
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logger->printf(" %d' to connect\n", port);
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}
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void loop() {
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//check if there are any new clients
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if (server.hasClient()) {
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//find free/disconnected spot
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int i;
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for (i = 0; i < MAX_SRV_CLIENTS; i++)
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if (!serverClients[i]) { // equivalent to !serverClients[i].connected()
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serverClients[i] = server.available();
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logger->print("New client: index ");
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logger->print(i);
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break;
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}
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//no free/disconnected spot so reject
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if (i == MAX_SRV_CLIENTS) {
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server.available().println("busy");
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// hints: server.available() is a WiFiClient with short-term scope
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// when out of scope, a WiFiClient will
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// - flush() - all data will be sent
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// - stop() - automatically too
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logger->printf("server is busy with %d active connections\n", MAX_SRV_CLIENTS);
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}
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}
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//check TCP clients for data
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#if 1
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// Incredibly, this code is faster than the bufferred one below - #4620 is needed
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// loopback/3000000baud average 348KB/s
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for (int i = 0; i < MAX_SRV_CLIENTS; i++)
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while (serverClients[i].available() && Serial.availableForWrite() > 0) {
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// working char by char is not very efficient
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Serial.write(serverClients[i].read());
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}
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#else
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// loopback/3000000baud average: 312KB/s
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for (int i = 0; i < MAX_SRV_CLIENTS; i++)
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while (serverClients[i].available() && Serial.availableForWrite() > 0) {
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size_t maxToSerial = std::min(serverClients[i].available(), Serial.availableForWrite());
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maxToSerial = std::min(maxToSerial, (size_t)STACK_PROTECTOR);
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uint8_t buf[maxToSerial];
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size_t tcp_got = serverClients[i].read(buf, maxToSerial);
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size_t serial_sent = Serial.write(buf, tcp_got);
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if (serial_sent != maxToSerial) {
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logger->printf("len mismatch: available:%zd tcp-read:%zd serial-write:%zd\n", maxToSerial, tcp_got, serial_sent);
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}
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}
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#endif
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// determine maximum output size "fair TCP use"
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// client.availableForWrite() returns 0 when !client.connected()
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size_t maxToTcp = 0;
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for (int i = 0; i < MAX_SRV_CLIENTS; i++)
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if (serverClients[i]) {
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size_t afw = serverClients[i].availableForWrite();
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if (afw) {
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if (!maxToTcp) {
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maxToTcp = afw;
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} else {
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maxToTcp = std::min(maxToTcp, afw);
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}
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} else {
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// warn but ignore congested clients
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logger->println("one client is congested");
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}
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}
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//check UART for data
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size_t len = std::min((size_t)Serial.available(), maxToTcp);
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len = std::min(len, (size_t)STACK_PROTECTOR);
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if (len) {
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uint8_t sbuf[len];
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size_t serial_got = Serial.readBytes(sbuf, len);
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// push UART data to all connected telnet clients
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for (int i = 0; i < MAX_SRV_CLIENTS; i++)
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// if client.availableForWrite() was 0 (congested)
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// and increased since then,
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// ensure write space is sufficient:
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if (serverClients[i].availableForWrite() >= serial_got) {
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size_t tcp_sent = serverClients[i].write(sbuf, serial_got);
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if (tcp_sent != len) {
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logger->printf("len mismatch: available:%zd serial-read:%zd tcp-write:%zd\n", len, serial_got, tcp_sent);
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}
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}
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}
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}
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